Susan M. Jalbert

Effects of different forms of dietary hydrogenated fats on serum lipoprotein cholesterol levels.

BACKGROUND Metabolic studies suggest that fatty acids containing at least one double bond in the trans configuration, which are found in hydrogenated fat, have a detrimental effect on serum lipoprotein cholesterol levels as compared with unsaturated fatty acids containing double bonds only in the cis configuration. We compared the effects of diets with a broad range of trans fatty acids on serum lipoprotein cholesterol levels. METHODS Eighteen women and 18 men consumed each of six diets in random order for 35-day periods. The foods were identical in each diet, and each diet provided 30 percent of calories as fat, with two thirds of the fat contributed as soybean oil (<0.5 g of trans fatty acid per 100 g of fat), semiliquid margarine (<0.5 g per 100 g), soft margarine (7.4 g per 100 g), shortening (9.9 g per 100 g), or stick margarine (20.1 g per 100 g). The effects of those diets on serum lipoprotein cholesterol, triglyceride, and apolipoprotein levels were compared with those of a diet enriched with butter, which has a high content of saturated fat. RESULTS The mean (+/-SD) serum low-density lipoprotein (LDL) cholesterol level was 177+/-32 mg per deciliter (4.58+/-0.85 mmol per liter) and the mean high-density lipoprotein (HDL) cholesterol level was 45+/-10 mg per deciliter (1.2+/-0.26 mmol per liter) after subjects consumed the butter-enriched diet. The LDL cholesterol level was reduced on average by 12 percent, 11 percent, 9 percent, 7 percent, and 5 percent, respectively, after subjects consumed the diets enriched with soybean oil, semiliquid margarine, soft margarine, shortening, and stick margarine; the HDL cholesterol level was reduced by 3 percent, 4 percent, 4 percent, 4 percent, and 6 percent, respectively. Ratios of total cholesterol to HDL cholesterol were lowest after the consumption of the soybean-oil diet and semiliquid-margarine diet and highest after the stick-margarine diet. CONCLUSIONS Our findings indicate that the consumption of products that are low in trans fatty acids and saturated fat has beneficial effects on serum lipoprotein cholesterol levels.

Lipoprotein Response to Diets High in Soy or Animal Protein With and Without Isoflavones in Moderately Hypercholesterolemic Subjects

Objective—The objective of this study was to assess the independent effect of soy relative to common sources of animal protein and soy-derived isoflavones on blood lipids. Methods and Results—Forty-two subjects with LDL cholesterol levels ≥3.36 mmol/L were fed each of four diets in randomized order for 6 weeks per phase. Diets contained a minimum of 25 g animal protein or isolated soy protein/4.2 MJ, with each containing trace amounts or 50 mg of isoflavones/4.2 MJ. Soy protein had a modest effect on total, LDL and HDL cholesterol, and triglyceride concentrations (−2%, P =0.017; −2%, P =0.042; +3%;P =0.034, −11%, P <0.001, respectively). Soy protein had no significant effect on plasma lipids in individuals with LDL cholesterol <4.14 mmol/L and significantly reduced total and LDL cholesterol and triglyceride concentrations in individuals with LDL cholesterol ≥4.14 mmol/L (−4%, P =0.001; −5%, P =0.003; −15%, P <0.001, respectively). No significant effect of isoflavones on plasma lipid levels was observed either constituent to the soy protein or supplemental to the animal protein. Conclusions—Although potentially helpful when used to displace products containing animal fat from the diet, the regular intake of relatively high levels of soy protein (>50 g/day) had only a modest effect on blood cholesterol levels and only in subjects with elevated LDL cholesterol levels (≥4.14 mmol/L). Soy-derived isoflavones had no significant effect.

TRL, IDL, and LDL Apolipoprotein B-100 and HDL Apolipoprotein A-I Kinetics as a Function of Age and Menopausal Status

Objective—To determine mechanisms contributing to the altered lipoprotein profile associated with aging and menopause, apolipoprotein B-100 (apoB-100) and apoA-I kinetic behavior was assessed. Methods and Results—Eight premenopausal (25±3 years) and 16 postmenopausal (65±6 years) women consumed for 6 weeks a standardized Western diet, at the end of which a primed-constant infusion of deuterated leucine was administered in the fed state to determine the kinetic behavior of triglyceride-rich lipoprotein (TRL), intermediate-density lipoprotein (IDL), and low-density lipoprotein (LDL) apoB-100, and high-density lipoprotein (HDL) apoA-I. Data were fit to a multicompartmental model using SAAM II to calculate fractional catabolic rate (FCR) and production rate (PR). Total cholesterol, LDL cholesterol (LDL-C), TRL-C, and triglyceride levels were higher (50%, 55%, 130%, and 232%, respectively) in the postmenopausal compared with the premenopausal women, whereas HDL-C levels were similar. Plasma TRL, IDL, and LDL–apoB-100 levels and pool sizes (PS) were significantly higher in the postmenopausal than premenopausal women. These differences were accounted for by lower TRL, IDL, and LDL apoB-100 FCR (P<0.05), with no difference in PR. There was no significant difference between groups in HDL-C levels or apoA-I kinetic parameters. Plasma TRL-C concentrations were negatively correlated with TRL apoB-100 FCR (r=−0.46; P<0.05) and positively correlated with PR (r=0.62; P<0.01). Plasma LDL-C concentrations were negatively correlated with LDL apoB-100 FCR (r=−0.70; P<0.001) but not PR. Conclusions—The mechanism for the increase in TRL and LDL apoB-100 PS observed in the postmenopausal women was determined predominantly by decreased TRL and LDL catabolism rather than increased production. No differences were observed in HDL apoA-I kinetics between groups.

Gender-Specific Differences in the Kinetics of Nonfasting TRL, IDL, and LDL Apolipoprotein B-100 in Men and Premenopausal Women

Objective—To investigate mechanisms underlying gender differences in serum lipoprotein concentrations, the kinetic behavior of apoB-100 was assessed. Methods and Results—Twenty subjects (<50 years; 12 men and 8 premenopausal women) were provided a Western diet for 4 to 6 weeks, after which the kinetics of apoB-100 in triglyceride-rich, intermediate-density, and low-density lipoprotein (TRL, IDL, and LDL) were determined in the fed state. Nonfasting plasma TC, LDL-C, and triglyceride concentrations were 23%, 34%, and 57% lower, respectively, in the women compared with men. Plasma TRL and LDL apoB 100 pool sizes were lower by 40% and 30%, respectively. These differences were accounted for by higher TRL and LDL apoB 100 fractional catabolic rates (FCR), rather than differences in production rates (PR). Plasma TRL-C and LDL-C were positively correlated with TRL and LDL apoB 100 concentrations and pool size, and negatively correlated with TRL and LDL apoB 100 FCR (women: r=−0.59, P<0.01 and r=−0.54, P<0.04, and men: r=−0.43, P<0.05 and r=−0.44, P<0.05). No significant associations were observed between plasma TRL-C and LDL-C and PR. Conclusions—These data suggest the mechanism for lower TRL-C and LDL-C concentrations in women was determined predominantly by higher TRL and LDL FCR rather than lower PR. This could explain, in part, the lower CVD risk in premenopausal women relative to men.